This is the card i would get if I were you. The 256 version isnt worth it.
Might as well get a 6800 128mb edition if you are spending that much.
But I just notice they day they are out of stock on those cards. Which isnt suprising since its a nice cheap card.
New Egg has it for the same price though.
I would recommend a 400W psu but 300W will be sufficient. No new fans unless you want more cooling.